v4 to v5 migration - performance issue

[simplecommerce]

Hi,

I was wondering if anyone could give me a hint or guide me on what to look at in my current project, as I am getting a weird behavior that is a bit difficult to debug.

I have migrated from v4 to v5 following the guidelines here https://mui.com/guides/migration-v4/.
In my current project, I am using the legacy styling solution.

In my v4 integration, when I click on my button to trigger opening of a dialog or menu, it is almost instant to render on screen.

In the v5 migration, it takes about 1-2 seconds to open and render on the initial open, afterwards it is instant.

I did it with a simple test, I removed all my content from the dialog and only left a "test" and that was pretty quick, but as soon as I put custom components or complex ones like forms, it is slow on the initial render and I have no idea why.

All your sandbox examples seem quick so I have no clue what is the issue.

Any hints on where to look is appreciated
I am unable to provide a sandbox demonstration as its a pretty big project.
Here are too captures to show the actual behavior.

v4: https://www.loom.com/share/7619e685bb1640b487e8df7ac96cee3d

v5: https://www.loom.com/share/b37c1934f57b445e9e86b058e2105382

[oliviertassinari]

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